Proposed Options for Noise Reduction from a Wastewater Treatment Plant: Case Study

Round 1

Reviewer 1 Report

The article is of general interest as a case study, but there are no novelties and no original contribution from the scientific point of view. The English language used in this article has many grammatical mistakes and my advice is to be revised by a specialist because is quite difficult to read and understand some expression.

The introduction is comprehensive, but similar works were shortly described without mentioning some of their conclusions or results.

In the beginning, there were identified as critical sources of noise on the site of the wastewater treatment plant the blower room, air distribution pipes, biofilter, sludge treatment, activation tanks, input pumping station. But till the end, only two types of sources suffered some measures to reduce the noise. What about the rest and how was made the discrimination between the sources?

In some places, the A-weighting is missing.

"160 The case study is aimed to research of noise effect of the wastewater treatment plan...".  - Actually, the study should be aimed at the noise effect on the people, even if it is generated by a plant.

"209 evening (50 dB) and night (45 dB)". - These levels are without any weighting?

'309  external stainless steel sheet with a thickness of 3 mm." - Why stainless steel and why the thickness of 3 mm?

"427  mathematical models were developed for a preliminary assessment of efficiency...".  - No mathematical model was developed in this article!

'429 On the basis of these noise maps, it was confirmed that the
above proposals will contribute to reducing noise...".  - A noise map cannot confirm but only predict or approximate something.

In Figure 19, where are presented the views of the blower room, before and after the application of measures, no difference can be distinguished. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The study is interesting but a major revision must be made before publication.

The suggestions are highlighted in the paper, please see the attached version of paper.

1. Please verify the grammar 
2. Regarding table 1: the tonality at 800Hz is not so clear from Table 1. The tonality correction is not indicating the freq of 800Hz. Maybe you can add a 1/3 octave spectrum or maybe a FFT which will indicate better this tone.
3. Fig 4. : in the text to said that there were 18 points but in Figure 4 there are only 15 points. Also, one point has no label.
4. Fig 6, please add the measurement unit dB or dB(A).
5. Regarding the numerical simulation. I suggest to add a whole chapter for these simulations where you must detail the boundary conditions. Please see the recommendations written in the document.
6. Please add more info regarding the measurement equipment. 
7. I would like to see more details regarding the technical solutions that were implemented in this station.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Main comment:

• Inconsistencies in introduction
• Non-logical sentences
• English needs improvement
• Methods section is missing and needs improvement
• What was the noise measurement equipment used for the point measurements (Table 2)?,
• What are the specifications and characteristics of the acoustic camera? How is it validated etc. should be described and relevant literature referred to.
• Which noise models were used, and what is the validity and accuracy?
• Several claims not adequately supported by references
• Article structure needs improvement. E.g. the chapter “Desciption of the problem” is mixed with text on methods and with part of the results. results.
• It is unclear why the measurements done before (acoustic camera) intervention and after intervention (noise mapping) were not identical. Why was the acoustical camera not used before and after intervention to show differences? So that figure 18 a and b and 19 ca and be could be show like Figure 6 respectively Figure 13 (left, before intervention) and a second ‘figure 13’ (right, after intervention) (possibly followed by evaluation of the immission levels by noise mapping, to assess the impact in the neighbourhood).
• The difference between figure 19a and 19 b is difficult to see.

Textual details:

Line 22: with the “ever increasing” population.. delete ‘ever’

Line 23: more and more people are exposed to the negative effects of noise. “ -> is this supported by evidence? Add ref.

Line 45: “Noise has become one of the major contaminants and one of the most common environmental problem.” -> Noise is not a contaminant. Check English. Add a reference.

Line 46/47: also … too.

Line 50: why speak about “it is possible to talk about acoustic smog or noise pollution.” Smog is usually used only for air pollution. Avoid the term ‘smog’.

Line 51: “can modify” replace with: may affect

Line 51: “and annoys” replace with: and may cause noise annoyance and noise induced sleep disturbance Miedema and Oudshoord 2001; Miedema and Vos, 2007, WHO, 2018

H.M.E. Miedema, C.M.G. Oudshoorn. Annoyance from transportation noise: relationships with exposure metrics DNL and DENL and their confidence intervals. Environ. Health Perspect., 109 (4) (2001), pp. 409-416

HME Miedema, H. Vos. Associations between self-reported sleep disturbance and environmental noise based on reanalyses of pooled data from 24 studies Behav Sleep Med. 2007;5(1):1-20.

World health Organization, Environmental Noise Guidelines for the European Region. 2018, WHO Regional Office for Europe: Copenhagen, Denmark.

Line 53: “and also nuisance.” Delete

Line 58: “creates an important part” check English. Do authors mean: forms an important part?

Line 55-58: Check for repetition.

“Environmental noise management presents an important part of the policy across the European Union context because industrial noise is a significant environmental problem for most of the cities 56 and urban population [3]. Environmental noise management creates an important part of the policy of the European Union because industrial noise is a major local environmental problem for most cities and urban population”

And please note: traffic noise is the main source of environmental noise exposure in urban areas, not industrial noise. This the authors also confirm themselves in line 60-63. Thus, “industrial noise is a major local environmental problem for most cities and urban population” may not be correct.

Line 72: “One of the important and major parts of noise pollution is caused by industrial sources of noise.” – Please correct: With 56 million people exposed to traffic noise, and 1 million to industrial noise, one could say traffic is the important and major source (not industry). It is also in contrast with line 78: “But by the mentioned document, the industrial noise presents in 78 comparison with other sources of noise the smallest contributor to population noise exposure.”

Line 73: “One of the important and major parts of noise pollution is caused by industrial sources of noise.” – Please add references to support these claims.

Line 74: “The level of noise which is generated by industrial equipment is influenced by many factors. These factors are related to the environment, …” – Please correct: The generation of the noise (the emission by the noise source itself) is NOT related to the environment. The environment affects the transmission of noise, and thereby exposure.

Line 75/76: “Industrial noises exposed around 800 000 people living in urban areas.” – Please check for inconsistency: IN line 63 the authors state: “1 million people suffer from the noise from industrial sources”.

Line 76: “The noise level is at least 55 dB during the day evening-night period.” – Where? This sentence seems meaningless? Noise immission levels show a gradient, with lower levels of exposure at greater distance from the source.

Line 77: “And around 400 000 people are exposed by noise levels of at least 50 dB during the night-time period” – Where? In Europe? In Slovakia?

Line 85: ”Industrial development, different and also, in some cases, chaotic locations of manufacturing facilities which are near residential areas demands to realize noise level monitoring” Please check sentence.

Line 87-89: Generally, the procedure of measurement of noise level is based on information on how to right to use the all industrial equipment, necessary time for measurement, the determination the variation of the noise level”” - Please check sentence

Line 95-99 “This author explained that the impact of vibration and related mechanical noise of industrial plants and also joining mechanical systems may cause significant influence for example to the reliability, productivity, durability and other significant parameters” – Please check sentence.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

One remark regarding Fig 5 which is still unclear, please correct it

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Main comments:

This paper describes an approach to assess noise emissions from industrial plants, to identify the main noise-sources, to apply a noise reduction intervention, and to assess its effectiveness in reducing noise exposure levels in the living areas in the vicinity of the industrial plant. While it may be valuable if it may aid noise reduction by inspiring others with a (low cost? easy to apply?) method, the scientific novelty remains unclear.  

Noise-emission-reduction is more commonly approached by such cycle (1 assessment of source strengths, 2 intervention, 3 evaluation of effect). If the novelty of this approach lies in the application of an ‘acoustical camera’ to assess noise emission source strengths, one would expect the authors would provide more arguments for the novelty of this instrument. However, the application of the acoustical camera is not clearly elaborated (e.g. with scientific papers which explain the concept, papers which describe the results of instrument validation, the accuracy and uncertainty in the measurement etc.). If the novelty lies in the use of an easy to apply, low cost method, one would expect that this would be elaborated more.

The input data for the noise mapping needs elaboration (needs to be specified).

How was the emission source strength after intervention obtained? (input for the after intervention noise mapping – for the prediction)

The importance of this paper is augmented by noise as a global problem. While this is true, it is hard to see the link with an approach to reduce noise from water waste treatment plants, since if any, this is a local problem (the main source of environmental noise exposure in living areas is traffic noise).

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Detailed comments and suggestions:

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48: “noise is possible to define” – “noise may be defined as” or “can be seen as”

51/52 Environmental noise management creates one of the most important parts of the policy of the European Union: replace “creates one of the most important parts of the policy” with: is an important aspect of the environmental policy of the…”

54: “is also now the END” replace with: is also referred to as the “END”.

55: The basis is to develop … (?)

57: “factors” replace with: elements?

62: “on the noise exposure level” do the authors mean: “on the noise emissions”. Please check.

63 “Nowadays, a widely used concept for improving the life standard is to reduce the industrial noise, above all in industrial and residential mixed areas” – check sentence: what do the authors want to say? Please clarify.

97: what is “the beamforming method”? Please specify.

101 – 113: what is the measurement uncertainty? Please add specifications and references.

117 “One of the demands of noise mapping is to ensure acoustic comfort conditions,”: What do the authors mean here? Noise mapping may be used to investigate noise exposure in living areas and to identify exceedance of noise exposure limits? Reduction of noise exposure below limit values is important to ensure acceptable noise levels, and thereby acoustic comfort?

122 “However, these studies are generally oriented to the area of transport, for example, railway  noise, airport noise, and road noise, as presented in [23–25]. Additionally, scientific research focused on the issue of industrial noise mapping is presented by many research papers.” – the first part of this sentence suggests limited information is available on industrial noise, while the second part contradicts that? PLease check and clarify.

125 to 134: It is hard to understand what the authors mean here: industrial noise mapping has been performed for decennia. Dedicated software for industrial noise mapping is widely available. Also commercial noise mapping software packages.

Methods:

Line 152 – 156 (sound visualization) – please add reference for this instrument, which provides the specs: How accurate is this instrument? Reference to scientific papers where it is applied? References to scientific papers in which the instrument is validated? What are its strengths and limitations? How often has it successfully been applied in similar settings and published scientifically  before (please specify and add  references).

2.3 Noise mapping: The input data for the noise mapping should be more clearly described.

Line 162: “the sound power data” do the authors mean: the noise emission source strength?

Line 182- 184: “This case study aimed to research the noise effect of a wastewater treatment plant because the influence of a wastewater treatment plant on the noise situation, as noise pollution is one of the major environmental global problems. A biological wastewater treatment plant is a source of such noise.”
This raises the question: What is the key aim of this study? The abstract suggests the aim is to propose a methodological approach which consists of 4 steps to (1) help identify the main noise emission sources for  industrial plants, to be used as a basis for (2) the development of noise abatement strategies, to 3) implement those noise emission reduction strategies for the main sources in an industrial plant, and 4) subsequently assess the successfulness of the applied measures by noise monitoring and mapping.

187: ‘” Residents of these villages complain about the noise caused by this wastewater treatment plant.” can this be quantified? Are annual complaint numbers registered?

236-237: day 50 dBA, evening 50 dBA; night 45 dBA, is this correct? Are noise levels expressed here in long term exposure levels: Lday, Leve and Lnight? If so: are evening (5dB) and night (10dB) exposure penalties applied?

Figure 5 now shows more measurement points. Several measurement points now appear twice on the map (e.g. M18 is allocated with 2 separate dots in different locations). Why is this? Still 1 noise measurement result is given. Were 2 measurements taken in the 2 M18 locations and was the average reported? This is confusing. The table states M18 is a point at 8 m from the source. However, if it is marked with 2 separate points, one would expect 2 different distances. Or were both 2 M18 points at 8m from a source? In line 241 the authors state measurements were taken at 18 locations (numbered M1 to M18) however, Figure 5 shows more points.

Figure 8 and figure 9 do not seem to match, while they both state they concern measurement 2?

From the figures showing the measurements with acoustic camera (e.g. figure 9, 11 and 12, figure 13) it is hard to understand the variation of noise emission in time. What was the measurement duration? How representative are these pictures for a 24h exposure?

439/440 – check sentence.

440 “A significant number of industrial noise sources are located near people’s residences”.- add references: how many people exposed to industrial noise above guideline values?

441: replace “concentrations”

441/442: “With the increasing concentrations of industrial noise sources, people are increasingly exposed to excessive noise, which is closely linked to negative effects on human health and a reduction in the quality of their housing.”- how is this claim supported? Any new industrial plant gets no permission unless it meets noise-exposure limits. Are there official figures which show an increasing trend (add refs)?

445 replace ” perfect knowledge of” with “insight in”

445 “using modern measuring instruments” – why “modern”? This does not necessarily mean more recently produced instruments are always better?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf